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1 DD7

A Uiz 17

Experiments in Educability

#)> STEVENSON SMITH

,4s Abstract of the thesis presented to the faculty of tht

Graduate School of the University of Pennsylvania

in partial fulfilment of the requirements

for the degree of Doctor of Philosophy

03s

REGULATION IN BEHAVIOR

Several years ago there appeared in Nature an account
of a statistical inquiry into sex determination. The results
indicated that children born to young mothers were predom-
inantly girls and that those born to old mothers were pre-
dominantly boys. Whether this hypothesis has been borne
out by further results I do not know, but assuming it to be a
law, it is an example of what has been called regulation in
behavior. The purpose which such a process serves is clear.
When there is a shortage of women in a community girls are
likely to marry when very young, due to the increased op-
portunity afforded them on account of the under-supply of
more mature women. If such marriages result in a number
of female infants greater than the normal expectation, the
balance between supply and demand is thereby reestablished.
A similar compensation is had when, in a society where fe-
males predominate, and hence are not married so early in
life, male offspring are in excess.

The world is full of instances of this sort. Organisms
utilize the very difficulties they encounter in order to bring
about the removal of these difficulties. Their make-up in-
sures this regulation. They do not depend on outside guid-
ance to carry them through adverse situations. The adverse
situations in combination with an organism are self-eliminat-
ing. Of course this is not always true for the individual,
but the social group, which is the larger organism, survives
because the procreation of its parts is as rapid as their
destruction.

We otten so construct a piece of machinery that this
principle of auto-adjustment holds in its behavior. This is
done so that we may not have to manipulate it and direct it
to any great extent. The floating ball disconnects the circuit
and stops the pump when the tank is full. The pendulum
swings to one side and releases the air pressure which tilts
the wing tip of the aeroplane when a gust of wind causes it
to pitch or roll, and this restores equilibrium. The electric

ONE]

310420

V*

sterilizer is supplied with a soft metal plug which melts off
and releases a spring, so breaking the circuit, when the water
is exhausted. Otherwise the rheostat would be burned out.
But now the heat prevents itself from being dangerous. A
general statement of these and other forms of regulation
might be valuable. It might indeed serve as a rule of thumb
for inventors.

Bancroft1 gives many excellent examples of regulatory
behavior as illustrating his "universal law." This law is
that "a system tends to change so as to minimize an external
disturbance." Some of the cases he notes are:

The readjustment of prices through supply and demand.

Tears caused by and discharging an irritating substance
from the eye.

A splinter causing its own sloughing out.

In chemistry, the occasional prevention of further re-
action by some reaction products.

An insult causing a response which may prevent further
insult.

The bending of trees to spill the wind.

It is certainly tautologous to say that organisms behave
along lines of least resistance, for our only definition of least
resistance is the resistance that a system is first to overcome.
But any suspicion that the statement of Bancroft's law falls
short in a like way of being a synthetic judgment, is removed
after he has clarified it by illustration and comment.

Adaptation of a group of animals or plants by selection
is a case of regulation if we regard the group as an organism.
The capacity for all the responses is not resident in all the
individual animals or plants, but is distributed among the
parts (individuals) of the entire organism (group). The
existence of the organism is maintained along with the life
of those parts which respond adaptively to the present con-
dition, notwithstanding the death of those parts which are
not adjusted so to respond. This is shown in the adaptation
of wheat to climate. A bushel of late ripening wheat will

i Bancroft, W. D., "A Universal Law," Jour, Am. Chem. Soc.,
XXXIII., No. 2, February, 1911.

[TWO

contain some grains of early ripening wheat. Planted under
certain conditions,, these latter alone will mature, but they
will serve as seed for the next crop, which will inherit their
characteristics for the most part, and which will be almost
entirely early ripening wheat.

When an apparently new structural adaptation is de-
veloped in an organism by a set of new conditions, the pre-
sumption is that the organism's capacity for this change of
structure was previously resident in the organism, and not
that the change was wholly caused by the new condition.
The condition was the necessary factor which had to be added
to the organism's potential capacity, in order that the adapta-
tion should result. An organism may in this way be so
adjusted as to respond adaptively to any one of a number of
possible conditions which may be mutually exclusive. So when
one response is realized, the others may be latent. This
is shown by the substitution of hair for wool in the coat of
a sheep that is taken to a warmer climate. In the domain
of behavior a similar rule is obvious. Here a given stimulus
calls forth a particular reaction which is especially fitted to
the situation.

The Vital Manifold

Organisms living in an environment of changing con-
ditions are, for the most part, constantly readjusting them-
selves to the change. They avoid bad conditions and seek
better. Or, when an unfavorable condition can not be avoided,
a change takes place in their structure which makes it pos-
sible for them to live in that condition. If, when in a certain
medium some metabolic change takes place in them, which
to be set right demands some other medium, they seek out
that other medium either by trial and error reactions or, fol-
lowing certain clues present in their surroundings, by some
specially appropriate instinctive or habitual reaction. If we
admit that such processes are regulatory, we have made a
beginning towards defining regulation. We may further say
that it is characteristic of organisms having a certain struc-

THREE]

ture. It is the result of the interaction of such organisms
and their media. The organism and the media constitute a
manifold which, though constantly operating, so functions as
to prevent disintegration of the organism. The life-long sta-
bility of arrangement possessed by the organism and its
offspring further differentiates it from the media and makes
most significant the distinction between biology and the
inorganic sciences. The field of the science of animal be-
havior of which the processes in such a manifold constitute
the data, is in part hardly to be distinguished from some of
the subject-matter of dynamic biology. The former science,
however, always classifies these processes on the basis of the
regulation which they display.

Negative Regulation

Regulation occurs when any process in the manifold
which reduces the stability of the organism results in such
a change, either in the media (through the organism's mi-
gration or otherwise) or in the organism itself, that the
stability of the organism is regained, so that the deviation
toward instability has come to be the cause of its own remedy.
Such regulation is the avoidance of those states in the or-
ganism or of those conditions in the media which are or have
become unfavorable to the stability of the organism, so let
us call it negative regulation.

Frequent examples of negative regulation are found in
the behavior of inorganic manifolds, of plants, and of the
lower animals. When a boat in a heavy sea rolls to one side
it rights itself into the perpendicular again. It does this
because of the fact that the further it tilts from the per-
pendicular the greater is the leverage by which the pull of
gravity, which tends to bring it back, is applied. Its behavior
conforms to our definition of negative regulation. The way
in which paramoecium retains favorable conditions must be
described by the same principle.2 The valve action at the
boundary of the optimum will work for the animal's good in

2Jennings, "Behavior of Lower Organisms."

[FOUR

either novel or familiar conditions. A river (organism)
shows regulation in migrating from its original channel to
one of greater stability, and in overcoming obstacles, such as
log jams or landslides, which serve as the cause of their own
remedy.

In the above examples correction is the result of the
excess of process, or deviation from stability. The correction
and the condition which needs correction may, however, both
be the results of the same cause, having no causal effect on
each other. For instance, in crayfish oxygen starvation is
corrected by the very activity which causes it, namely, walk-
ing. The gills are placed so as to be moved by the legs,
for which reason walking causes both depletion and repair
of the oxygen content of the blood. Another example is
found in the protective color changes in the coat of northern
mammals. These changes are possibly not the result of the
color environment (the seasonal variation of which is a devia-
tion toward instability), but rather the result of some ac-
companying condition such as food or temperature plus certain
internal factors. That is, the brown fur does not become
white because of the whiteness of the snow. The cause to
which is due in part the occurrence of the snow, namely, a
decrease in temperature, is largely responsible for the adapt-
ive change in the color of the fur. Again, for example, the
sunshine which on a summer day would otherwise overheat
a man, is in part the cause of the breezes which assist in
keeping him cool. The cause, that is, which produces the
deviation from the optimum brings about also a condition
which helps to restore the optimum.

We may then occasionally find this relation between
the deviation from stability and its means of correction. The
mutual cause of these two processes may indeed be in-
definitely remote. This phase of regulation is not recog-
nized in the above definition, so we may add: Negative regu-
lation also occurs when a process in the manifold which is
the cause of a deviation from stability results independently
in its correction.

FIVE]

Positive Regulation

An organism may be so constituted that it reacts to some
condition which is favorable, adapting itself so as to obtain
benefit from it, even when failure so to react to the condition
would cause it no more harm than the loss of an unusual
benefit. This form of reaction is sometimes given to a con-
dition which the organism does not reach by locomotion,
such as a condition which is generally periodic and has no
fixed spacial position ( e. g., a weather condition). But if
the organism has means of locomotion, the reaction more
usually involves a movement toward the favorable condition.
This favorable condition may be only occasionally present
or it may be only occasionally needed by the organism. The
favorable condition to which the organism reacts may be at
a distance from, or may impinge upon, the organism. If it
is at a distance it must act mediately upon the organism and
the organism must have the power of locomotion in order to
take advantage of it. The favorable condition may be rela-
tively fixed in space, such as air at the top of the water, or
it may be relatively fixed in time, such as the regular re-
currence of sunlight. To distinguish this form of regulation
let us call it positive.

Positive regulation occurs when some change in the en-
vironment or in the physiological state of the organism causes
such an adaptive reaction of the organism or such an alteration
in the media that the interaction of the newly arranged
organism and media which follows brings about increased
stability in the organism. In such a process both organisms
and media have a double function. The media act first as
the stimulus to the organism's adaptive reaction and second
as a contributing cause of the increased stability of the
organism. The organism likewise must be set or arranged
to adjust or orient itself to the changed conditions and also
to interact with the novel media so as to cause increased
stability in the new relation. The squirrel's storing its food,

[SIX

the butterfly's seeking its mate, and the prospector's digging
for gold are all examples of positive regulation.

In positive regulation the favorable condition and the
adaptive change do not always have the direct relation of
cause and effect. They may be as well results of a single
cause. This is especially true in the higher forms of be-
havior, such as the behavior of a group of sympathetic
organisms in a colony or society. For instance, Greek phil-
osophy was a cause which has ramified into many results.
Largely because of it, and of the development which it
caused, the present-day students write their books on science
or philosophy, because of it there are laboratories, without
which these books would have lacked much material, and
printing presses, without which the volumes would never have
reached their readers. That same early philosophy is the
inheritance of the people and without it the modern book
would not be understood. As another example, when the
hot weather in spring impels birds to migrate northward it
causes also those changes in the country further north which
produce food and the proper conditions for raising the young.
So we may add: Positive regulation occurs when a process
in the manifold which is the cause of some potentially favor-
able condition results independently in an adaptive change
by which the organism takes advantage of it.

Both positive and negative regulation may take place as
the result of a change merely in the physiological state of
the organism and not be due to any variation in the media.
Negative regulation is seen under such conditions in the
reactions of the over-fed sea anemone away from food, or in
behavior of a dog that after a time moves further away
from a fire the heat of which had at first attracted him.
Positive regulation takes place under like conditions when
respiration is increased due to exercise, or when the hungry
animal goes out to search for food to which previously it
had been indifferent. Judgment and reason in the higher
animals furnish the best examples under these conditions for
positive regulation. Positive regulation usually results in an

SEVEN]

increased margin of stability which is insurance against
future dangers and permits the organism some rest from
the activities of negative regulation. The two forms of
regulation are combined in the food reaction of most an-
imals. Hunger results in migratory search after food as
well as in its capture. Many animals, however, capture
food for future use when the conditions of negative regu-
lation are not present. The two forms of regulation are,
for instance, combined when a man rises in the morning partly
because he is no longer comfortable in bed and partly be-
cause he hears the water running into his tub.

The direct interaction between the conditions existing
at any given time as well as the resulting adaptations in the
manifold may be described as follows:

In negative regulation unfavorable media (present or
at a distance) may cause a change in the organism that
makes it either resist such media, or avoid or migrate from
such media, or analyze or synthesize such media into in-
nocuous or favorable media. Or some unfavorable part or
process in the organism may cause its own elimination or
discontinuance, either by interaction with the media, or by
action within the organism, or by both of these.

In positive regulation favorable media (present or at
a distance) may cause a change in the organism that makes
it either interact with such media or enter into or migrate to
such media. Or innocuous media (present or at a distance)
may cause a change in the organism that makes it analyze or
synthesize such media into favorable media. Or some favor-
able part or process in the organism may cause its own main-
tenance or continuance, either by interaction with the media
or by action within the organism or by both of these.

[EIGHT

EXPERIMENTS IN EDUCABILITY OF
PARAMOECIUM

Reactions to Touch. The purpose of the following ex-
periments was to determine what kind of modi f lability is
shown by Paramoecium due to recurring experiences of the
same kind. For this purpose first a capillary tube was se-
lected of a bore smaller than the length of the Paramoecium
and larger than his width. The animal was caught by the
upward suction of the tube and the tube was then placed on
a movable carriage, so the animal could always be kept in
the field of the microscope no matter what part of the tube
it might be swimming through.

Once in the tube the Paramoecium swims to the forward
end and upon reaching the meniscus jerks backward for
several times its own length, then approaches again in a wider
spiral than before. This backing and approaching takes
place at least a dozen times and later the Paramoecium set-
tles down to a pecking movement, revolving anti-scriwwise
about the meniscus and attacking about five places in its
circumference.

In the original approaching and retreating both move-
ments may be either screwwise or anti-screwwise. In ap-
proaching, both the screwwise and anti-screwwise movements
give about the same width of spiral, namely, a very slight
one. If the retreat is made anti-screwwise a relatively
straight course is followed, the spiral being hardly notice-
able. If the retreat is screwwise a very wide spiral re-
sults.

In most cases the animal after a varying time bends its
anterior end around toward the aboral side, forming a "U"
with its body, and after a number of jerks succeeds in re-
versing the position of its body in the tube. In all cases it
turns toward the aboral side, thus using the long creeping
cilia near the buccal groove to obtain a hold on the side of
the tube.

NINE]

As this facing about in the tube is repeated, the time
taken for each turn may be longer than for the last, the
animal finally dying of apparent fatigue, or, if the tube is not
so small that too violent an effort is required of the animal,
the time may gradually be shortened and a most surprising
aptitude of turning be developed. Paramoecia from a vig-
orous culture give better results than poorly nourished ones.
Under optimum conditions there was \found a reduction of
turning time, after the animals had been in the tube for
twelve hours or more, from four or five minutes to a second
or two, which is the minimum time* , in which the turn can
be made.

Often the Paramoecium will rest for a long period at
once meniscus, slowly circling around with its buccal groove
resting against the air surface. When, however, the effort
is made to reverse, the shortening of time in the practiced
individuals is very apparent.

Reactions to temperature. In these experiments a
capillary tube was selected large enough to allow the Para-
moecia to reverse their direction without touching its
sides, and in which two Paramoecia could pass each other
without difficulty. A number of individuals were taken up
in this tube and the tube was placed on a carriage having
two large glass supporting tubes through which water of
different temperatures was passing and on which the
capillary tube rested.

While hot water was flowing through one support and
cold water through the other the temperatures could be re-
versed, so that the cold water would flow through the one
and the hot water through the other. Thus the distribution
of temperature in the capillary tube could be reversed. By
cold water is meant water at normal temperature to which the
animal gives no reaction.

As soon as the capillary tube is heated at one end by
contact with the hot support, the Paramoecia at that end
dart about at random until they are headed toward the cool
end of the tube and even then do not swim to the cool end

[TEN

at first but often turn back to the hot end several times be-
fore finally swimming over to the cool water. Once ar-
rived at the cool end the Paramoecia do not stay there, but
turn and start back to the hot water. In this way a
Paramoecium may traverse the length of the tube a dozen
times or more before coming to rest at the cool end of the
tube. As the animals leave their resting place at the warm
meniscus in obedience to the repeated reversing of tem-
peratures in the tube, their movements become slower and
more regulated and they seldom turn more than once toward
the cold water before swimming in that direction. It is not
significant to express this modification of behavior in terms
of time for, although the time involved in getting away from
the heated end of the tube is somewhat reduced as the
stimulus recurs, it is the suitability of the movement to ac-
complish the result which characterizes the later reactions.
In these the actual locomotion, is slower but the random
movements give place to more determined ones.

The influence of an associated past experience upon the
reaction to a given stimulus. Although in the following ex-
periments the observations gave nothing but negative results,
these results serve to fix the limits of educability in Para-
moceium. Although Paramoecium profits by experience, as
seen in the above sections, it does not show associative memory
such as Loeb would demand as the criterion of consciousness.

The conditions of the first experiment were these. Para-
moecia were placed in a trough having an extremely thin
glass bottom and this trough was immersed in a partitioned
box containing hot and normally cool water on the two sides,
so that the bottom of the trough was kept cool on one half
and warm on the other. There was a distinct line, not cor-
responding exactly to the partition of the under box, at
which the Paramoecia approaching from the cool side would
turn back. A light was fixed above the trough and a screen
interposed so that a shadow fell covering the warm area and
a minute part of the cool area beyond the reaction line.
The white Paramoecium which was here used, gives no re-

ELEVEN]

action to light or darkness and it was hoped that by allow-
ing the animals to experience darkness whenever they ex-
perienced heat they might, when the heat was removed, re-
act negatively to darkness. This they did not do, however,
though one group of Paramoecia were allowed to experience
the two conditions together for fifteen hours, one for
twenty-four hours, and one for forty hours.

Another experiment of a somewhat similar kind was
performed in which it was tried to bring about the associa-
tion of heat and gravity. A small tube was bent into an
L shape and, after some Paramoecia had been drawn up into
it, was placed so that one leg was horizontal and the other,
rising from this, was vertical. At the top of the vertical leg
was placed a hot metal rod in contact with the glass and
kept at a constant temperature. If Paramoecia show
geotropism, (More: Am. Jour. Phys., vol. 9, pp. 238 ff.)
this irritability to gravity should be more easily associated
with heat than could light, which, although it must make
some impression on the organism, does not cause normally

an avoiding reaction.

Whenever, the Paramoecia swam up the vertical leg of
the tube they received a heat stimulus which caused them
at first to jerk backwards and after many random trials to
swim downward to the cool water. Although these conditions
were kept unchanged for as long as three days the Paramoecia
never learned to avoid the vertical leg of the tube. In the
end they did not react as violently to the heat and did not,
as at first, swim occasionally past the hot metal rod. Also
they seemed later to develop greater sensitivity, reacting to
the heat before getting as close to the metal rod.

CONCLUSION

Paramoecium is educable in that its behavior may be
modified to show the results of practice, both in a reduction
of the time involved in performing a movement and in the
increase in suitability of the movement to accomplish the
appropriate result.

[TWELVE

In so far as the tests here apply, there is no evidence
of associative memory in Paramoecium.

The reversing movement above described is in the
nature of a positive reaction.

THIRTEEN]

SOME RESULTS OF TRAINING A GUINEA PIG

Description of the Maze.

The maze used in these experiments consisted of a
straight passage which ran for eighteen inches from the
entrance to a point where two other passages turned at
right angles from it, running to the right and to the left.
Three inches beyond this point the right passage turned
again to the right and the left passage to the left, both open-
ing through doorways into an area outside the maze.

Doors were made of sheet zinc and were swung from the
top. The exit doors could open only outward and the entrance
door could open only inward. Thus the animal having entered
the maze could pass out through the exit doors. These
doors were provided with hooks by which either could be
locked at will. The outside measurement of the box was
seventeen by twenty-six inches.

In order to pass through the maze the animal enter-
ing had to choose either the right or the left passage. This
choice was involved in most of the following experiments
with the maze. An albino male Guinea pig was used as the
subject in these tests. He was about four months old when
first used and about seven and a half months old when the
tests ended.

Habit Formation in the Maze.

The Guinea pig had been accustomed to come to the edge
of his cage, when the side of it was rapped on, in order to
get a bite of carrot which was held in the experimenter's
hand. In this first experiment the carrot was held in the
first passageway of the maze and knocked frequently against
the wooden side. The Guinea pig being outside the entrance
door, reacted, as he had learned to do in his next box, by
hunting about for the carrot in the neighborhood of the
source of sound.

After the pig had learned to enter the entrance door
he was allowed to do so and here to eat a little of the carrot,

[FOURTEEN

which was then removed and rapped against the wood beyond
the right doorway. The left doorway was locked. After
the first trial, rapping to indicate the position of the food
was left off. The carrot was shifted back and forth and
the time taken by the pig to follow through the respective
doors was recorded. This measurement began when the
pig had just finished chewing one mouthful and was reach-
ing for another, the carrot being removed at that time. The
measurement ended when the animal had passed through the
door and it had fallen shut behind him. Thus there were
two series of measurements; one of the time taken to enter
the maze and one of the time taken to leave it. These are
expressed in the following table. The trials in each series
were taken consecutively, a period of several hours elapsing
between the series.

Into Maze No.TrialsAv. of All A. D. Av. Firsts. A.D. 1st Trial

Series 1 11 168.9 222.6 553. 324.7 1040.

Series 2

Series 3

Series 4

Out of Maze

Series 1

Series 2

Series 3

Series 4

Series 5

Series G

The measurements in all the tables are given in seconds.

Antagonistic Habit Formation and Cross Training.

After an interval of one hundred and three hours, the
Guinea pig was returned to the maze. This time the right
door was locked and the left door was unlocked. There
was no difference in appearance, that would be noticeable
to the pig, between the maze now and before, because the
means of locking the door was a wire nail, driven into the
wood at the side of the door and bent to an angle of ninety
degrees, which could be turned so as to prevent the door
from swinging and was visible only from the outside. A
turn in the direction opposite to that which the Guinea pig
had learned had now to be made before he could leave the
maze. The carrot was concealed until the Guinea pig had
left the maze and was then given him as a reward.

FIFTEEN]

4

22.8

11.8

14.

7.3

3.

5

5.

1.6

6.3

1.1

5.

8

27.1

36.7

6.

3.3

4.

11

69.

75.8

208.

69.3

312.

4

20.5

18.2

20.

24.

3.

5

4.2

1.8

4.3

2.4

8.

8

34.4

44.1

6.3

3.1

5.

10

59.1

49.9

19.3

3.8

25.

18

8.4

3.4

3.7

1.1

4.

In the following table is noted the time and accuracy of
the guinea pig's forming the antagonistic habit of making the
left turn. Only his reactions in leaving the maze are noted,
his entering being disregarded. Fractions are omitted, the
next higher whole number being used.

Series No. Trials Av. Time A. D. % of Errors

1 6 113 165 50

2 11 11 14 9

3 4310

4 17 2 1 0

After an interval of forty-eight hours the conditions of
the first part of the experiment were resumed, namely, the
left door was locked and the right door was left open. The
results are shown in the following table.

Series No. Trials Av. Time A. D. % of Errors

1 15 11 7 41

2 7520

After an interval of six hours, the conditions were again
reversed. In the following table are shown the confusion
effects.

Series No. Trials Av. Time A. D. % of Errors

1 15 22 19 67

2 25 9 4 40

3 11 8 3 37

The Guinea pig seemed to compensate for his inability
to form the left turn habit, as previously, by his greater
quickness in making a practical trial of both doorways. He
learned that if one door was locked the other was open and
he substituted a method of trial and error for the docility of
the former experiments. Further, he acquired a negative
reaction to the sight of the locked door, which he remembered
was locked often without trying it, that took the place of the
lacking positive reaction to the unlocked. The general con-
clusion from the above results is that frequent alternation
of the opposite conditions reduces the adaptability of the
Guinea pig for either of the these conditions when it is
afterwards maintained constantly. This last method of re-
action of the Guinea pig's was well suited for the experi-
ments in Movement-odor Association described in the fol-
lowing section.

[SIXTEEN

Movement-odor Association.

A watch glass covered with a perforated sheet of zinc
was placed at the end of the long passage at which point the
Guinea pig had to choose between the right and left turns.
When the left door was open the watch-glass contained a
piece of absorbent cotton saturated with oil of peppermint.
When the right door was open this watch-glass was replaced
by another containing tincture of assafoedita. Care was
taken that the two watch-glasses should offer the same visual
appearance and also that the maze should be well aired be-
tween each change. As the time of the turning reaction was
so largely dependent on the pig's state of hunger and fatigue
the measurement was of right and wrong cases only, no record
being taken of the time.

At first twenty-four series of three trials each were
taken, the odors and the unlocked doorways being alternated
every three trials. The Guinea pig was considered to have
failed in every trial in which he tried the locked doorway.
No punishment was used at the locked door.

Considering the first six series and the last six series
under each of the two conditions, making groups of eighteen
trials each, the results were as follows:

Peppermint and Left Turn Per cent of Right Cases

First six series 55.5

Second six series 38.8

Average 47.15

Assafoedita and Right Turn Percent of Right Cases

First six series 44.4

Second six series 50.

Average 47.7

Average of all 72 trials 47.4

The above series extended through two weeks. During
the next eight days seventy-two more trials were taken,
equally distributed between the two conditions, that is, be-
tween the occurrence of assafoedita and the open right door
and peppermint and the open left door. In these trials a
random order of presenting the conditions was used, but the
same set of conditions never occurred more than twice con-
secutively. The results were as follows:

SEVENTEEN]

Percent of Right Cases

Peppermint and left 58.3

Assaf oedita and right 47.2

Average 52.7

The Guinea pig showed that he detected the difference
between the assafoedita and the peppermint for he would
often draw back from the assafoedita and then pass it rapidly,
always taking care to jump over the watch-glass. He usually
acted in this way when the assafoedita was first presented
after an interval of some hours, and he never acted so
toward the peppermint.

The results are not ground for assuming that the
Guinea pig benefited at all from the practice, although the
practice was equal in amount to that which was sufficient
for creating the spatial association of the previous experi-
ment.

Experiments to determine the guinea pig's ability to
give different specialized reactions to two sounds were
negative.

Experiments to determine the Guinea pig's ability to
associate different end terms with two series of motor re-
actions, gave fairly positive results, showing the characteric
reduction of time and errors.

[EIGHTEEN

SOME RESULTS OF TRAINING A WHITE MOUSE

An albino mouse was used in these practice experi-
ments. The conditions were as follows:

A drop-bridge apparatus was used which consisted of a
disc of pasteboard mounted on an inverted glass tumbler, on
the top of which the animal could walk about but from
which he could not descend. There was a hinged bridge which
could be propped up out of reach of the animal but which
might be lowered by pulling a string which passed above the
disc. The string was attached at one end to a fixed rod and
at the other to the prop which held up the bridge. The prop
was made in the form of a toggle joint, the system being
barely in equilibrium. This made necessary only a slight
pull on the string in order to cause the bridge to descend, and
the position of the prop was so adjusted as to require just
slightly more than a chance touch on the string to bring about
the fall.

When the bridge had descended it formed part of an
incline which led to the ground, where food was provided.
There were two motives which might lead the animal to come
down from the disc; the presence of the food below, and the
restlessness or general diffusion of energy which caused the
animal to move about.

At the first few trials, the mouse tried to descend by
climbing down the sides of the tumbler, but he found this
impossible. As a result of his random movements he finally
(after 165 seconds) pulled the string and the bridge fell into
place. To this he paid no attention, apparently not realizing
that it led to the ground. Twice, before he at last managed
to climb down the bridge, he ventured along it a few steps
but returned to the disc on top of the tumbler.

The most rapid practice results were seen in the habit
of descending the bridge after it had been dropped, the
habit of pulling the string being slowly and never perfectly
learned, that is, the mouse always combined the characteristic
climbing-down movement with the string pulling. He would
get his nose over the string and then lean over the edge of

NINETEEN]

the disc, making scrambling movements with his feet. He
need not have leaned over so far, as the bridge dropped with
less pull on the string, and he could have omitted, for the
most part, the foot movements, so that the reaction was not
reduced to the greatest efficiency.

These movements, however, were always made on the
side where he could reach the string, even though he some-
times wandered about the disc at random. After a lapse of
five weeks he did at first revert to his old attempts to climb
down anywhere, but this reaction was soon corrected.

In the following table are stated both the time the mouse
took to drop the bridge after being placed on the disc and
the time he took to descend to the ground after the bridge
had been dropped.

TABLE

Series

No. Trials

Dropping
Av. Time*

Bridge
A. D.

Descending
Av. Time A. D.

1

6

58

53

37

42

2

8

27

14

41

47

3

3

12

5

5

1

4

3

10

4

6

2

5

3

11

5

9

2

6

4

18

11

7

2

7

6

13

9

10

5

8

5

13

8

14

11

9

3

12

6

9

2

10

4

10

6

8

3

11

3

38

10

80

42

12

6

24

16

36

47

13

4

10

6

7

2

14

5

6

3

9

5

*Time given in seconds.
The time elapsing between the tenth and the eleventh
series was five weeks, whereas that between all other adjacent
series averaged twenty-two hours, with a maximum interval
of thirty-six hours.

[TWENTY

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